Existing continuous carburizing furnace systems are designed to perform a particular carburizing process. Systems capable of performing multiple carburizing processes are run on a batch basis, i.e. one process at a time.
Existing continuous carburizing furnace systems include different chambers for separating the various steps of the carburizing process, i.e. heating, carburizing, cooling, equalizing and quenching. For example, U.S. Pat. No. 4,763,880 issued Aug. 16, 1988 describes a furnace system having, in sequence, a preheat chamber, a rotary carburizing chamber, a rotary diffusion chamber, and a rotary equalizing chamber. A cooling chamber, a batch quench chamber and a press quench chamber are connected to the equalizing chamber. While this system can process parts requiring different heat treatment cycles, the system is limited to performing substantially non-carbide processes (i.e. where the intent of the process is not to form high volume fractions of free carbides in the surface region of the microstructure). The system processes different parts to different case depths with or without quenching. It cannot, for example, perform a carbide process such as described in Canadian Patent No. 610,554 issued Dec. 23, 1960, or as described in U.S. Pat. No. 4,921,025 issued May 1, 1990.
It is desirable to have a system which can perform multiple carburizing processes simultaneously in a continuous type furnace system; for example a carbide process together with a substantially non-carbide process.